Neutron irradiated hydrocarbon conversion process



Nov. 8, 1960 R B. LONG ET AL NEUTRON IRRADIATED HYDROCARBON CONVERSION PROCESS Filed June 21, 1956 HYDROCARBON FEED CRACKING CATALYST CONTAINING B OR U6 2 w I i i l l i i 4 NEUTRON fll I IRRADIATION i i i I Lkf'f: SEPARATION :f-TTIEJ PRODUCT Robert 8. Long Robert W Housmm iflvemors Henry J. Hibshman John P. Longweil By a3. a mmmay NEUTRON IRRADIATED HYDROCARBON CONVERSION PROCESS Robert B. Long, Wanamassa, N.J., Robert W. Houston, Durham, N.H., and Henry J. Hibshman, Plainfield, and John P. Longwell, Westfield, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed June 21, '1956, Ser. No. 592,985 9 Claims. (Cl. 204-154 This invention relates to hydrocarbon radiochemistry and more particularly, to the conversion of petroleum hydrocarbons by neutron irradiation in the presence of an acid center hydrocarbon conversion catalyst which is impregnated with a material that, upon neutron capture, yields appreciable quantities of alpha particles of high kinetic energy.

This application is a continuation-in-part of Serial No. 547,860, Hydrocarbon Conversion Process, filed November 18, 1955, by the present inventors and now abandoned.

In brief compass, this invention proposes an improvement of a process wherein hydrocarbons are converted in a reaction zone by neutron irradiation in the presence of an acid center hydrocarbon conversion catalyst, or cracking catalyst. The improvement of this invention comprises impregnating the cracking catalyst with a neutron-capturing, alpha-emitting material which acts as an accelerator and reaction modifier. An important feature of this invention is that the conversion of the hydrocarbons is carried out at moderate temperatures, i.e., temperatures below 600 F.

A number of highly desirable reactions can be carried out by exposing materials to high intensity ionizing radiation, such as beta and gamma rays and neutrons. The use of radiation to effect certain reactions afiords a number of substantial advantages over conventional prior art practices.

It has also been known to convert hydrocarbons, such as petroleum naphthas and gas oils, by the application of pressure and temperature under the influence of conversion catalysts that aid in controlling the selectivity or course of the reaction. Such processes as naphtha reforming or hydroforming, gas oil cracking, and residua coking or hydrogenation are well known in the petroleum industry.

It has now been found that by impregnating a cracking catalyst with a material that has the ability to capture neutrons and emit highly ionizing alpha particles, here called an (n, a) material for convenience, an improved radiochemical catalyst is obtained. The cracking catalyst, and thus the conversion, are profoundly influenced by the presence of the (n, a) material. In use this catalyst greatly accelerates the reaction.

It has also surprisingly been found that in the irradiae tion of hydrocarbons in the presence of acid center cracking catalysts impregnated with '(n, a) material, the catalysts exert an unexpected appreciable influence on the selectivity, even when the reaction temperature is relativelymoderate, i.e., the temperature is substantially below incipient thermal cracking or conversion temperatures. According to this invention, the presence of an acid center cracking catalyst containing an (n, a) material in an irradiated hydrocarbon reaction mixture, re sults in unexpected advantages.

It has further been found that the catalyst of .this intion. It has been found that hydrocarbon feed stocks that contain a large proportion of hydrocarbons that are not unduly branched are polymerized quite readily.

This invention is applicable to a wide range of hydrocarbon feed stocks, including conventional petroleum oils, shale oils, tar sand oils, asphalts, synthetic oils, and natural and artificial hydrocarbon gases. It has the greatest use in the conversion of petroleum derived oils such as whole crudes, distillate and residual fractions therefrom, extracts or concentrates therefrom, and mixtures thereof. As later developed, however, a significant advantage is obtained by irradiating certain select feed stocks. A preferred feed stock is a hydrocarbon oil boiling in the range within the limits of 500 to 1100 F. that is predominantly composed of material which is not unduly branched and is amenable to polymerization. By

ventiou favors certain types of reactions, e.g., polymeriza- J not being unduly branched is meant that little or none of the feed stock contains molecules with a tertiary carbon atom.

This invention is concerned with impregnation of conventional cracking catalysts of high surface area. The catalyst can basically comprise materials such as silica, alumina, zirconia, titania, magnesia, and mixtures thereof. These catalyst materials can be derived from natural sources or can be manufactured. The materials can be used as bases or distending agents for smaller amounts of more active catalytic components. Such catalytic components can comprise elemental metals, metal oxides, sulfides, chlorides, phosphates, chromates, and other salts and mixtures thereof.

The catalyst used preferably has a particle size under about 1000 microns, but may be much larger in size if desired, e.g., one inch or more. The surface area of the catalyst is in the range of 50 to 600 m. /gr., and the pore size is in the'range of 20 to 150 A. The catalytic and carrier materials used are normally those which, upon neutron bombardment, produce radioisotopes having short half lives, i.e., less than 10 weeks and preferably less than one Week, or have small neutron capture crosssections so that very little of the material becomes radioactive.

' The (n, a) materials used according to this invention are those isotopes that upon capture of a neutron, usually one having an energy below e.v., produce alpha particles of high kinetic energy, greater than 0.1 m.e.v., which have tracks of high ion density. Of primary interest are boron 10 and lithium 6, although other materials can be used such as Fe, oxygen 17 and zinc 67. The cross-section of the (n, a) material used is preferably, above 100 barns.

When the term boron is employed in this specification; it is intended to mean naturally-occurring boron. However, the novel results of the present invention are due to an interaction between neutrons and the isotope boron 10, which isotope is present in naturally-occurring boron to the extent of about 19 wt. percent. When the term lithium is used, it is intended to mean naturallyoccurring lithium which contains Li to the extent of about 8.0 wt. percent, which reacts Li (n, :1) H Concentrates of these isotopes can, of course, be used.

While, broadly, these (n, on) materials have similar properties, they also have individual differences that can cause difierent results, particularly with specific reactions. For example, the higher neutron capture cross-section of boron 10, its lower alpha energy, and the difference in recoil particles as compared to lithium 6, often causes it to give different results than lithium 6. Boron l0 and lithium 6, however, when impregnated on the acid center cracking catalyst have, in common, the ability to greatly accelerate the neutron irradiated conversion reaction and to affect the active centers of the cracking catalyst.

The (n, a) materials, when employed in this invention, can be present in the form of elements, and/or as compounds. The catalyst is usually impregnated with an (n, or) compound, which then, for example, can be calcined to form the oxide or reduced. In some cases, the (n, or) material cannot only be distended 'on a base material, but alsocan be compounded or mixed with the base.

It is believed that the alpha emission by the (11,a) material, besides ionizing the reactants, profoundly influences the catalytic centers of the catalyst whereby unusual and substantial advantages are obtained.

Specific compounds of boron which are useful in this invention include: inorganic borates and boric acid, boron halides such as BF or Bclg, boranes, alkyl borates, B and borax.

Specific compounds of lithium which are useful include: LiNO LiHCO LiCH LiC H lithium phenol and lithium aluminohydride.

The catalyst can be used as a suspension in the hydrocarbon reactant, or as a fixed, fluid, or gravitating bed, all of which methods are known in the art. The catalyst, if contaminated, as by carbon deposition, can be regenerated by known methods such as burning, acid treating, chemical reworking, and the like. The catalyst can be regenerated in place or external of the reactor, and either continuously or periodically, as the need arises.

This invention is based in part upon the important finding that hydrocarbon conversion catalysts display an appreciable effect on selectively at moderate temperatures, i.e., at temperatures below 600 F. This means that it is now possible to operate at lower temperatures, heretofore unattractive because of the slowness of the reaction rate. This permits the obtainance of reactions and selectivities not previously possible.

This invention is applicable to conversion reactions wherein the reactants are wholly or partly in the gas, liquid or solid phase. It is most advantageously used with liquid phase reactions and the pressure used is, therefore, preferably sufficient to maintain substantially liquid phase conditions.

The process of this invention can most convenientlybe carried out, particularly on a commercial scale, byemploying a nuclear reactor. The process can be carried out either on a batch or a continuous basis. The present process is preferably carried out with some type of agitation or continuous flow, so that there is suflicient contact between the oil, the ionizing radiation, and the sub-divided catalytic solid. To carry out a continuous process, the material to be irradiated can be simply pumped through the pile itelf, or through pipes disposed in the pile. In some instances, the hydrocarbon reactant can also serve as a moderator. I

The drawing attached to and forming a part ofthis specification schematically illustrates this invention.

In the drawing, a hydrocarbon material, e.g., a distillate virgin gas oil, is introduced into the process by line 1. A catalyst, e.g., a finely divided silica-alumina cracking catalyst containing B supplied by line 2 from source 3, is mixed with the feed material. The resulting mixture is then passed through radiation source 4.

The amount of (n, a) material used is dependent upon the neutron flux and more particularly, the concentration of the material in the reaction mixture is inversely related to the neutron flux. This relationship can be expressed as follows:

C- Fa where C is the concentration of (n, a) isotope expressed in wt. percent in the reaction mixture,'F,-, is the neutron flux expressed as neutrons/cmF/sec, and K isa factor expressing the relationship between C and F,,. It is preferred that K have a value in the range of 10 to- 10 preferably 10 to 10 forboron 10,'and values in the range of S 10 to 5 X 10 preferably 5 X10 to 5 X 10 for lithium 6.

Preferably the concentration of boron in the reaction mixture is about 0.001 to 1.0% by weight based on the total reaction mixture, and for lithium is 0.001 to 5.0 wt. percent. Lesser or greater concentrations can be employed if deisred. These concentrations refer to the concentration of the element per se, whether it be in metallic form or in the form of a compound thereof. These concentrations, based on wt. percent of the catalyst, are usually in the range of 0.05 to '10 wt. percent for the normal catalyst/oil ratios used. A preferred form of this invention is to use a'sufiicient amount of an (n, a) ma terial on the catalyst which provides at least 10% of the energy absorbed by the hydrocarbon reactant or oil.

The radiation from the atomic pile consists primarily of neutrons and gamma rays. The neutron flux used is preferably above about 10 neutrons/cm. /sec., and the gamma ray flux is preferably above about 10 roentgens/hr. The present process is most effectively carried out employing slow neutrons, i.e., neutrons having an energy less than about e.v. Preferably, the majority of the neutrons are slow neutrons. Moderators such as carbon, light or heavy water, or hydrocarbons can be employed, if desired, to obtain the desired proportion of slow neutrons.

Although a 'suspensoid system is shown in the drawing, i.e., the solids are carried by the hydrocarbon reactant through the reaction zone, the conversion catalyst can exist as a fixed, fluid or'gravitating bed within the radiation zone 4. With fluid beds, the pipes containing the reactant and catalyst preferably pass vertically through the pile with upflow of the fluid reactants.

The irradiated material is transferred by line 5 to separation zone 6. The separation zone comprises means for recovering the catalyst such as by distillation, filtration, absorption, and chemical reaction. The recovered catalystcan be directly recycled by line 7 if desired, or can be first treated as by burning, steaming, etc. to remove contaminants and/ or improve its properties before being recycled. The concentration of the (n, a) material can be maintained by addition of fresh catalyst, addition of suitable compounds with the feed, or by reimpregnating the recycled catalyst, either continuously or periodically.

The hydrocarbon products are also separated in zone 6. Thus with a gas oil feed, distillation, extraction, or absorption, as With-molecular sieves, can be used. If desired, some of the hydrocarbon product can be recycled by line 9.

Separation zone 6 can also include means for removing and/or neutralizing radioactive waste products. Such means can include storage tanks to permit decay of radioactivity, ion exchange apparatus, distillation columns and solvent extraction units. The finished product is removed from the-process by line 10.

The following examples serve to further illustrate this invention.

The air cooled, natural uranium, graphite moderated research reactor of the Brookhaven National Laboratories wasused for these tests. This pile was operating at a total power of about 24 megawatts at the time, which gave the following flux distribution at the point where the oils were irradiated:

Slow neutron flux (.03 e.v.)

:25 X 10 neutrons/cmF/sec. Fast neutron flux 1 m.e.v.)

:05 X 10 neutrons/cmF/sec. Gamma intensity=1.7 X 10 roentgens/ hr.

The core of the reactor'was approximately a 20 ft. x 20 ft. x 20 ft, lattice of graphite with'horizontal oneinch diameter aluminum-clad uranium rods spaced evenly throughout the reactor extending from the north to south faces 'ofthe'core. This corewas completely surrounded by Shit of concrete shielding. The sample holes used for irradiation were horizontal 4-inch x 4-inch square holes extending through the 5 ft. concrete shield and into the carbon core for a distance of '10 ft. from the core face. Normal operating temperatures in the experimental hole were from 250 to 400 F.

Radiations were carried out as follows:

Three one-quart samples were irradiated at one time by placing them in three vented 3-inch diameter aluminum containers which were mounted on a horizontal aluminum sled. The vents of aluminum tubing extended from the vapor space in the containers out of the core and through the shielding to a sample receiver system where gases and condensable liquids were metered and collected. The samples were prepared by adding the solids to the container to fill it, evacuating the void space in the container, and sucking the oil into the container with the vacuum. The samples were then purged with purified nitrogen and inserted in the pile during scheduled shutdowns. After irradiation for ten days, they were withdrawn from the pile during the next shutdown.

The catalysts used in these examples were prepared as follows:

1. BORIA ON ALUMINA The alumina base was prepared in a manner similar to that taught by Kimberlin in U.S.' Patent No. 2,636,865. An alumina alcoholate was prepared by dissolving pure aluminum metal in alcohol. A 99.95+% pure alumina was obtained fromthis alcoholate by precipitating with water, washing, and drying. The alumina was made in the form of Az-inch diameter granules which were calcined. These granules were impregnated with a water solution of boric acid, dried at 600 F., and calcined for four hours at 800 F. This catalyst had a surface area of 300 m. /gr. and a pore size of 50 to 80 A,

2. BORIA ON SILICA-ALUMINA Alumina was precipitated from aluminum sulfat solution on previously precipitated silica, by the addition of ammonia. The precipitate was then washed, dried, and calcined for several hours at temperatures up to 1200" F. It contained 13% alumina. It was pulverized and made into the form of x -inch diameter pills. These pills were impregnated with boria as described with the alumina catalyst. The catalyst had a surface area of about 500 m. /gr.

3. LITHIUM ON SILICA-ALUMINA The silica-alumina pills described in 2 above were impregnated with lithium by absorbing a 0.7 N lithium nitrate solution, after the catalyst had been calcined at 900 F. for five hrs. The catalyst with the absorbed LiNO solution was heated for about 20 hours at 850 F. to dry the catalyst and oxidize the nitrate to lithium oxide.

Three oils were treated with these catalysts. oils were:

Oil A.-A petroleum virgin parafiinic gas oil having the following inspections: Gravity of 307 API, Bromine No. of 1.25 centigrams/ gram, 34.4 SSU viscosity at 210 F., viscosity index of 67, and 0.14 wt. percent sulfur content. The distillation characteristics were 5% ofi at 600 F. and ofl at 700 F, at atmospheric pressure.

Oil B.A petroleum virgin naphthenic gas oil having the following inspections: Gravity of 31.1 API, Bromine No. of 2.47 centigrams/gram, viscosity of 33.0 SSU at 210 F., viscosity index of 77, and 1.5 wt, percent sulfur content. The distillation characteristics were 12.6% 017 at 600 F. and 98% off at 676 F. at atmospheric pressure.

Oil C.-A phenol extract of'a catalytic cycle stock (560700 F.), obtained by cracking a heavy West Texas gas oil. This extract contains polynuclear aromatic compounds and has a 11.4 API gravity and a sulfur content of 1.6 wt. percent. 90% of the extract boiled in the range of 600-700 F. at atmospheric pressure.

These Table l 011 A 011 B Oil 0 0 15% B 0.5% Li 2 Si/Al 2 Si/Al Days Irradiated 10 14 Conversion to 03-, Wt. Percent"-.. 7. 4 9. 7 22.1 Products:

Boiling Range 0/430 0/430 0/430 Percent on Feed 2. 6 3. 4 0. 1 Sulfur, Wt. Percent. 0.04 0.04 Vol. Percent Aroruat 21.3 14. 7 57. 4 18. 4 21.3 66.9 66.7 13. 8 430/600 430/600 430/600 5.6 4.9 5. 8 0. 05 0. 04 0. 15 23. 9 15. 9 18.0 63. 6 24. 9 40. 4 12.5 59. 2 41. 6 30. 8 36. 4 34.0 52. 8 10. 1 13. 5 104 600/676 600/676 600/676 38. 5 20. 7 7. 9 Sulfur, Wt. Percent 0. 06 0.10 0.03 Gravity, API 6.0 26. 3 Bromine N o 15. 2 Aniline Pt., F 137 144 Boiling Range- 676/900 700/900 660/700 700/900 700/900 Percent on Feed. 13. 5 6. 2 1. 8.1 11.9 Viscosity, SSU 210 F 54. 2 66. 5 52. 4 46. 3 Pour Pt., F 15 5 Boiling Range" 900/1, 005 900/970 700/900 900/970 900/960 Percent on Feed- 9. 7 6. 5 15. 0 10.4 4. 3 Viscosity, SSU 210 F 191. 4 154. 8 46. 9 317. 9 Pour Pt., F 30 25 10 Boiling Range 676+ 1, 005+ 970+ 900+ 970+ 960+ Percent on Feed 46. 0 38. 3 35. 7 55. 8 41.0 37. 9

l Al-Alumlna. Si/Al-Silica-alumlna.

The data in the above table show that catalysts containing boron and lithium have very striking effects on the products obtained from diiferent types of oils. The silica-alumina catalyst results in greater feed conversion as indicated by the amount of feed remaining. In addition, the catalyst results in greater amounts of saturates at the expense, primarily, of olefins produced and somewhat reduced yields of aromatics. The inspection of the liquid product with the boria catalyst showed a marked increase in viscosity which indicates extensive polymerization.

The rate of reaction was increased about 25-fold as indicated by the initial rate of gas evolution, when an (n. a) material impregnated on a catalyst was used. This accelerating effect is very important because it results in a much more economical process.

These data also indicate that the boron on alumina is a specific catalyst for cracking saturated hydrocarbons to highly unsaturated materials. The data also indicate that the combination of an acid center cracking catalyst with boron appears to be a specific catalyst for converting naphthenic gas oils to high quality diesel oils, as determined by diesel index.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. In a process of converting normally liquid hydrocarbons in a reaction Zone by neutron irradiation in the presence of an acid center hydrocarbon conversion catalyst, the improvement which comprises impregnating said catalyst with an (n, a) material.

2. The process of claim 1 wherein the conversiontemperature is maintained below 600 F.

3. The process of claim 1 wherein said (11, a) material comprises an isotope selected from the group consisting of lithium 6 and boron 10.

4. The process of claim 1 wherein the conversion pressure is sufiicient to maintain substantially liquid phase conditions.

5. The process of claim 1 wherein said hydrocarbon 8 comprises a petroleum gas oil boiling in the range of 500 to 1100 F. and said catalyst has a surface area in the range of to 600 m. gr.

6. An improved petroleum oil conversion process which comprises irradiating a hydrocarbon oil with neutrons at an intensity above 10 neutrons/cm. /sec., at a temperature below 600 F. While in intimate contact with an acid center hydrocarbon conversion catalyst impregnated with an (n, a) material which provides at least 10% of the energy absorbed by said hydrocarbon oil.

7. An improved hydrocarbon conversion catalyst for neutron irradiated hydrocarbon conversion processes, which comprises a highly porous acid center cracking catalyst impregnated with an (n, a) material.

8. The catalyst of claim 7 wherein said (11, a) material is selected from the group consisting of boron 10 and lithium 6.

9. The catalyst of claim 7 wherein said acid center cracking catalyst is selected from the group consisting of silica, alumina, zirconia, titania, magnesia, and mixtures thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,338,709 Sulzberger May 4, 1920 2,350,330 Remy June 6, 1944 2,377,744 Bailey June 5, 1945 2,424,152 Connolly July 15, 1947 2,743,223 McClinton et a1. Apr. 24, 1956 FOREIGN PATENTS 665,263 Great Britain Jan. 23, 1952 OTHER REFERENCES Davidson et a1: A.E.C. Document MDDC-1449, November 12, 1947.

Davidson: Jour. of Applied Physics, vol. 19, pages 427-433, May 1948.

Mincher: A.E.C. Document KAPL-731, pages 3-7, April 2, 1952, declassified February 15, 1955. 

1. IN A PROCESS OF CONVERTING NORMALLY LIQUID HYDROCARBONS IN A REACTION ZONE BY NEUTRON IRRADIATION IN THE PRESENCE OF AN ACID CENTER HYDROCARBON CONVERSION CATALYST, THE IMPROVEMENT WHICH COMPRISES IMPREGNATING SAID CATALYST WITH AN (N, A) MATERIAL. 